In the related art, an electric power steering apparatus that applies a steering auxiliary power (i.e., assist torque) from an electric motor to an in-vehicle steering mechanism has been proposed.
For example, PTL 1 discloses a technique in which two systems of torque sensors are provided in an electric power steering apparatus, a torque sensor where an abnormality occurs, among the two systems of torque sensors, can be identified, and in addition, a steering assistance can be stably continued based on a detection value of a torque sensor where the abnormality is not detected.
Further, in the related art disclosed in PTL 1, a failure monitoring part sets deviations (51 Tr1-Trx|, |Tr2-Trx|) between an estimated torque Trx calculated by an estimation torque computing part and steering torques Tr1 and Tr2 detected by the torque sensors as reliability levels. Then, a target assist torque Tas* is set by using a steering torque detected by the torque sensor having a lower reliability level.